Electrical heating apparatus



w. M. RoBERDs ELECTRICAL HEATING APPARQTUS Filed June so, 194s mm J Y.

Feb. 19, 1946.

weslc M. E C@ Gttorncg Patented Feb. 19, 1946 ELECTRICAL HEATINGAPPARATUS wesley M. noberds, oomngswobd, N. J., sslgmr to RadioCorporation' of America, a corporation of Delaware Application June 30,1943, Serial N0.' 492,817`

8 Claims.

This invention relates to electrical heatingl apparatus, and moreparticularly to inductive heating apparatus for rapidly heating the workto be treated.

The use of radio frequency electrical energy for rapidly heating variousarticles is now Well known. In heating metallicarticles, as forhardening the surfaces thereof, there is usually employed an inductor orcoupling coil in the form of a tubular member 'through which coolingfluid is passed for cooling the applicator coil or inductor. In general,where the outside surface of an article is to -be heated, the coil isplaced around the article, whereas if the inside surface is to beheated, as in the case of a Cylinder bore of an internal combustionengine, the applicator is placed within the bore. In any case, the workis scanned by the coupling coil by moving one relative to the other atan appropriate rate.

In many instances, the work to be scanned is of such small diameter atthe surface to be treated that the use of an applicator ring or aninductor kof the type conventionally employed with radio frequencycurrents is not feasible, since coils of small diameter are diilicult toform out of hollow or tubular conductors, Thus, for ex ample, where thebore of a rifle is to be hardened by inductive heating at sufficientlyhigh power from a source of radio frequency electrical energy, theconventional applicator or inductor is not suitable because it cannot beformed satisfactorily on a sufciently small diameter.

invention, the applicator or coupling coil proper is constituted by asplit copper ring ymounted at y the end of a Bakelite or-other suitablenon-conbore in the cylindrical guide so as to provide an.

annular spacev therebetween through which the cooling fluid may bepassed, The bore in the guide and the split rod are both suitablytapered adjacent their ends so as to insure spraying of the coolingWater against the inductor ring ask it leaves the device.

The novel features that I consider characteristic of my invention areset forth with particu- The primary object of my present invention is toprovide an improved coupling inductor which is free from the abovementioned disadvantage.

More particularly, yit is an object of my present invention to providean improved coupling inductor which is particularly suitable for use inbores of small diameter.

Another object of my present invention is to Y provide an improved`coupling inductor as aforesaid which can be readily manufacturedby-machine methods and which. therefore, can be made with greataccuracy.

Still another object of my present invention ls to provide an improvedinductor as set forth larity vin the appended claims. The inventionitself, howeven. both as to its organization and method of operation, aswell as additional objects and advantages thereof, will best'y beunderstood from the following description of one embodiment thereof,lwhen read in connection with the accompanying drawing, inwhich:

Figure 1 is a central sectional vview of a heating unit formed inaccordance with my present invention,

Figure 2 is a front elevation thereof, and

Figure 3 is a sectional view taken on the line III--III of Figure 2.

Referring more particularly to the drawing,

wherein similar reference characters designate corresponding partsthroughout, there is shown i a tubular support I to one end of which issecured a split ring 3 of copper or the like, as by. means of cement 4or other suitable adhesive.

The support I is formed with a bore 5 which, at

above which can be readily cooled by a fluid k cient in use.

In accordance with one form of myspresent least in part, tapersoutwardly as it approaches the applicator ring 3.

Within vthe bore of the support I is a split Copper rod constituted bythe parts Iva .and 1b, the rod being concentric with the support I andthe ring 3, but being of a smaller diameter than the bore 5 whereby toprovide an annular space or passage 5a between the rod 1a, 1b and thewall of the bore 5,' as clearly seen from Figures l and 3. The rod 1a,'Ib is tapered similarly to the bore i, the tapered portions 1c thereofterminating at points short of that end of the support I to which thering l is secured. Beyond the tapered portions 'Ic, each of the rodparts 1a, 'Ib' continues on a smaller diameter and, at the extreme end,

each of the parts 1a, Ib is bent at right angles to provide offsetportions 9a and 3b, respectively, which extend radially of theapplicator ring 3. One of the offset terminal portions 3a is secured toone terminal of the applicator ring 3, and the other offset portion 9bis secured to the other terminal of the ring 3, as best seen in Figure2.

Thus, the main portion of each of the rod parts 1a, Ib extendslongitudinally along the support I, whereas each offset portion 9a, 9bis disposed substantially` radially within the inductor 3. A strip I Iof mica or other suitable insulating material is inserted between theparts la and 1b.

For connecting the applicator ring to a source of radio frequencyenergy, there is connected to the support I by cement or the like I2 atubular conductor I3 which, together with a second tubular conductor I5connected to the rod part 1a, constitutes a concentric line. 'Ihe outerconductor I3 terminates in an enlarged, outwardly threaded portion I1 onwhich a threaded cap I9 is received. A pair of insulated bushings 2|between which a soft rubber washer 23 is confined serve to maintain thetubular conductors I3 and I5 in concentric relation. By threading thecap I9 onto the portion I1 tight against the bushings 2 I, the washer 23is compressed to form a fluid tight connection between the conductors I3and I5. The rod part 'Ib is connected to the outer conductor I3 by'ablock of conducting material 25, which may be soldered thereto, and by ascrew 21. Connection of the concentric line I3, I5 to a source of highfrequency electrical energy 29, such as a vacuum tube oscillationgenerator operating at radio frequency, may be made through a couplingtransformer 3| in well known manner.

For heating the wall of a bore 33 of the work 35, the support I isinserted into the bore 33 in engagement with the wall of the bore. Theapplicator coil 3 is of somewhat smaller diameter than the outsidediameter of the support I, wherefcre the support I acts as a guide formaintaining the ring 3 in concentric relation with the bore 33. Whenpower is applied and the device is moved along the bore 33, current inthe inductor 3 induces heating current in the work which rapidly heatsthe wall of the bore 33 to the desired temperature. Scanning may beperformed at whatever rate is found suitable. For cooling the applicatorcoil 3 and also the work (as for quenching) a cooling fluid, such asWater, may be forced l a taper which converges or tapers inwardly awayfrom the support I. Thus, the cooling fluid is sure to strike at leastthe tapered portion of the tube 3 after which it may or may not bedeflected onto the Work for cooling thelatter, depending upon the angleof taper of the coll 3. With this arrangement, much more cooling fluidmay be utilized than in conventional coils constructed of tubularconductors.

From the foregoing description, it will be apparent that have providedan improved heatunit which is compact, simple in construction, highlyefilcient in use. The various parts of the device can be readilymachined and they are, therefore, much more uniform and accurate thanthe tube coil types of applicators. l'urthermore, by proper selection ofthe diameter of the supporting tube I and the applicator ring 3, boresof various sizes. can be treated with the present invention. Also, bymerely selecting proper lengths of concentric line I3, I5, it isapparent that bores of various lengths may be adequately treated.

Although I have shown and described but one embodiment of my invention,it will, no doubt, be apparent to those skilled in the art that manyother modifications thereof, as well as changes in the one describedherein, are possible. I therefore desire that my invention shall not belimited except insofar as is made necessary by the prior art and by thespirit of the appended claims.

I claim as my invention:

l. In inductive heating apparatus, the combination of a tubular supportof insulating material, a coupling coil secured to one end of saidsupport and adapted to be brought into inductive relation with the workto be heated, said support having a bore at least part of which tapersoutwardly toward said coil, and a pair of conductive members within saidbore secured to the terminals of said coil and adapted to connect saidcoil to a source of electrical energy, said members being formed atleast in part on a taper similar to that of said bore but being spacedfrom said support whereby to provide a passage for the reception ofcooling fluid, and said coil having a portion located in the path ofmovement of cooling fluid passed through said passage.

2. Heating apparatus according to claim i characterized in that thetapered portions of said members terminate at points short of that endof said support to which said coil is secured, said members continuingbeyond said points on a smaller diameter.

3. Heating apparatus according to claim 1 characterized in that saidcoil tapers inwardly away from said support.

4. Heating apparatus according to claim 1 characterized in that saidcoil tapers inwardly away from said support, and characterized furtherin that the tapered portions of said members terminate at points shortof that end of said support to which said coil is secured, said memberscontinuing beyond said points on a smaller diameter, and the taper ofsaid members being such as to direct the cooling fluid onto at least thetapered portion of said coil.

5. Heating apparatus according to claim 1 wherein said coil isconstituted by a single-tum, annular member, and wherein each of saidconductive members includes a portion disposed substantially radiallywithin said annular member.

6. Heating apparatus according to claim 1 wherein said coil isconstituted by a single-turn, annular member, and wherein each of saidconductive members includes a main portion extending longitudinallyalongsaid support and an offset portion disposed substantially radiallywithin said annular member, said offset portions being secured one toeach of the terminals of said annular member.

7. In inductive heating apparatus, the combination of a tubular supportof insulating material, acoupling coil secured to one end of saidsupport and adapted to be brought into inductive relation with the workto be heated, a pair of conductive members Within said support eachsecured to a separate terminal of said coil, said members being spacedfrom said support whereby to provide a space therearound for the passageof cooling fluid, and a concentric line for external connection of saidcoil to a source of high frequency electrical energy, said linecomprising inner and outer tubular conductors the outer one of which issecured to said support and is connected electrically to one of saidconductive members and the inner one oi which is connected electricallyto the other one oi said conductive members, one of said concentric lineconductors having communication with said space whereby cooling fluidforced into said last mentioned conductor will also be forced throughsaid space.

8. Heating vapparatus according to claim 'l g wherein said innerconductor is the one which has communication with said space.

WESLEY M. ROBERDB.

